Field of the Invention
The present invention relates to mobile communication.
Discussion of the Related Art
3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) that is an advancement of UMTS (Universal Mobile Telecommunication System) is being introduced with 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE adopts MIMO (multiple input multiple output) having maximum four antennas. Recently, a discussion of 3GPP LTE-A (LTE-Advanced) which is the evolution of the 3GPP LTE is in progress.
As set forth in 3GPP TS 36.211 V10.4.0, the physical channels in 3GPP LTE may be classified into data channels such as PDSCH (physical downlink shared channel) and PUSCH (physical uplink shared channel) and control channels such as PDCCH (physical downlink control channel), PCFICH (physical control format indicator channel), PHICH (physical hybrid-ARQ indicator channel) and PUCCH (physical uplink control channel).
Meanwhile, the PDCCH is monitored in a limited region called a control region in the subframe and further, a CRS which is transmitted in an entire band is used to demodulate the PDCCH. As the type of control information is diversified and the amount of the control information increases, the flexibility of scheduling deteriorates only by the existing PDCCH. Further, an enhanced PDCCH (EPDCCH) is introduced in order to reduce a burden caused by the CRS transmission.
On the other hand, in a next-generation mobile communication system, it is predicted that a small cell having small cell coverage will be added into coverage of a macro cell.
However, when multiple small cells transmit the EPDCCH onto the same PRB, the multiple small cells can interfere with each other.